RFR: 8357086: os::xxx functions returning memory size should return size_t [v15]

[Stefan Karlsson]

On Wed, 30 Jul 2025 14:28:16 GMT, Anton Artemov <duke at openjdk.org> wrote:

>> Hi,
>> 
>> in this PR the output value types for functions which return memory are changed, namely:
>> 
>> 
>> static julong available_memory(); --> static bool available_memory(size_t& value);
>> static julong used_memory(); --> static bool used_memory(size_t& value);
>> static julong free_memory(); --> static bool free_memory(size_t& value); 
>> static jlong total_swap_space(); --> static bool total_swap_space(size_t& value);
>> static jlong free_swap_space(); --> static bool free_swap_space(size_t& value); 
>> static julong physical_memory(); --> static bool physical_memory(size_t& value); 
>> 
>> 
>> The return boolean value indicates success, whereas the actual value is assigned to the input argument. The following recommended usage pattern is introduced: where applicable, and unsuccessful call is logged. 
>> 
>> Later, the return value can be attributed with `[[nodiscard]]` to enforce the pattern.
>> 
>> Tested in GHA and Tiers 1-5.
>
> Anton Artemov has updated the pull request incrementally with one additional commit since the last revision:
> 
>   8357086: Addressed reviewer's comments

We try to refrain from adding TODO / FIXME comments in the code. If there's something that really needs to be done we tend to put that into a JBS issue instead.

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Changes requested by stefank (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/25450#pullrequestreview-3072048580